Sensors come in many shapes and sizes, from motion detectors that signal lights to go on when we enter a room to Geiger counters that detect radiation loss. Sensors are used in commercial, industrial, and personal applications including cars, machines, aerospace, medicine, manufacturing, and robotics. Often, sensors help regulate and control existing operations, such as proximity sensors that assist in aircraft and marine applications and speed and position sensors that assist in automotive engine management. Current sensors monitor AC and/or DC current for different electrical systems. Some current sensors provide highly accurate current measurement values and other current sensors quickly detect a high overdrive (ODR) current.
Often, sensor signals are small, such that sensors need to have very low offset values and very low noise values. Sometimes, to reduce offset errors, preamplifiers or analog to digital converter (ADC) input stages chop or modulate the input signal. However, chopping the input signal causes high frequency chopper noise that needs to be filtered, which consumes area on the integrated circuit chip. Also, dynamic error effects convert the high frequency chopper noise to signal frequencies and cause residual offsets and in-band noise, which reduces the dynamic range of the sensor and increases the ratio of the smallest accurate signal to the biggest signal. Analog feedback loops can be used to reduce offset error. But, analog feedback loops consume more area on the integrated circuit chip, where the low-pass filtering frequency is small in comparison to the chopper frequency to avoid influencing the signal in the forward path.
For these and other reasons there is a need for the present invention.